Insulated wire



Patented June 9, 1936 UNITED STATES PATENT OFFlCE INSULATED wnm ofDelaware Application August 14, 1930, Serial No. 475,235

1 Claim. (Cl. 173-264) This invention relates in general to certain newand useful improvements in insulated wires or conductors, and moreparticularly to insulated conductors such as are used'in telephoneswitch- 5 board wiring, and the principal object of the invention is toprovide an insulated electric wire which has high insulation qualities,and is cheap and economical to manufacture.

A further object of the invention is to provide an insulated electricwire which occupies a minimum of space in a cable comprising a pluralityof conductors, so that a larger number of conductors may be employed ina cable which is of relatively the same size as that formerly utilized.I a

A further object of the invention resides in the provision of aninsulated electric conductor having ahigher degree of insulation valuethan that formerly provided without employing additional impregnatingcompounds and insulating materials formerly required to insulate theconductor.

Wires or conductors have heretofore been insulated by coveringconductors with one or a 25 plurality of alternate layers of silk andcotton,

. cord or threads, each layer of which is usually wound in oppositedirections. In addition, these several layers of silk and cotton threadshave been rendered more moisture proof by being impregnated with aninsulating compound, such as boiled beeswax, after the conductors havebeen previously baked in an oven at a very high rate of temperature toinsure that no moisture remains in them. This method of manufacturinginsulated wires or conductors is expensive and requires great care tosee that no moisture remains in the insulating silk and cotton wrapping,and in addition expensive machinery is required to place this coveringonto the wire. In

ping and the sealing wax for insulating the conductor all contributes tothe relatively. high cost of this type of insulated conductor.

It is an object, therefore, of this invention to dispense with bakingprocess and the use of the beeswax for insulating conductors andlikewise to employ a cheaper and more satisfactory winding or braidingcovering for the wire.

' A feature of the invention therefore resides in 50 the use of, acellulose orother organic or fibrous material for use in wrapping theconductor. This covering is then impregnated with a solution of acetoneto partially dissolve the cellulose material so as to amalgamate thewhole coveri'ng into a homogeneous mass onto the conductor.

addition, the cost of the silk and cotton wrap- The solution of acetonepartially dissolves the cellulose material and converts it into amoreor-less hard covering on the conductor which adheres tenaciously toit by shrinking slightly onto the conductor.

An electrical conductor insulated in this manner is impervious tomoisture, has a higher degree of insulation value than ordinary waxedsilk and cotton insulation, occupies a, much smaller area in a cable, isvery flexible and heat resistant, and finally, is more economical tomanu-- facture.

The above objects and others, not specifically pointed out, will bereferred to hereinafter in connection with the drawing which illustratesa preferred embodiment of the invention, although it will be understoodthat any number of modifications will be apparent to those skilled inthe art, and although only a single insulated conductor has beenillustrated, it will be apparent that any number of similar insulatedconductors may be combined into a single cable of any capacity.

Referring to the accompanying drawing, the numeral 5 indicates a singlecopper wire or conductor such as is usually employed in switch.- boardwiring and telephone apparatus. The conductor, or wire 5, if desired,may be covered with a primary insulation covering consisting of a hardbaked coating of a residiuum of an oil or enamel. However, this primaryinsulating coating may be entirely dispensed with. A wral ping Icomprising a plurality of threads of a cellulose material is then woundupon the conductor. This cellulose, or other similar inorganic compound,is very easily formed into threads as is well known and is commonlyknown under the trade name of Rayon or artificial silk. A singlecovering of any number of threads may be provided on the conductor, butit is occasionally desirable that a plurality of layers of the cellulosematerial be wound upon the conductors, each layer being wound in anopposite direction from the preceding layer, for example, the layer ofthread I may be wound upon the conductor I in one direction, while thenext layer of thread such as 8 is wound upon the conductor in theopposite direction. On top of the layer of cellulose material 8 anadditional layer 9 of similar material may be wound upon the conductorin the same direction as the wrapping I. The wrapping of cellulosematerial I upon the conductor 5 or the additional wrappings 8 and 9 areapplied in a well-known manner, and it is not thought necessary toexplain in detail the manner in which this is accomplished.

has the characteristic of chemically reacting on the inorganic cellulosematerial so that it amalgamates into a homogeneous mass onto theconductor 5. The wrapping l of cellulose material after having beentreated with the acetone prescuts a high glossyfinish and tightlyadheres to the conductor 5 due to the shrinking action of the materialafter having been treated.

If desirable, the additional wrappings 8 and 9 of cellulose material orrayon silk which may be wrapped upon the layer 1 are in turn treatedwith acetone in a similar manner as the layer of wrapping I. Theapplication of the acetone to the wrapping 8 amalgamates the wrappingwith the wrapping I and binds the same into a solid mass by .thedissolving action of the acetone. If further wrappings are required onthe conductor, the wrapping 8 is applied on top of the wrapping 8 in theopposite direction from it, and this in turn is likewise treated with asolution of acetone to convert the last wrapper into a mass with thefirst two wrappers I and 8.

After having been treated with the solution of acetone, the insulationupon the conductor 5 has the appearance as indicated at ID by theconductor acquiring a smooth hard-finish which is heat resisting andmoisture proo'f, clings tenaciously to the conductor in a manner similarto the anamel 5, does not crack when bent, is an excellent insulator,and due to the shrinkage action of the cellulose material, after havingbeen treated with the acetone, requires a very much smaller space when aconductor treated in this manner is inserted in a cable.

A plurality of these conductors may be, bound together to form a cableof any proportion. In cables it is usually necessary that the individualwires making up the cable be provided with certain identifying meanswhereby the various conductors may be attached to certain electricaltelephone apparatus such as is used in the telephone art, and for thispurpose each conductor has a particular color of thread runningthroughout its entire length, and as the Rayon" silk or cellulosematerial may be very easily dyed in different colors, the method ofidentifying the conductors is easily effected with this invention.

In previous types of cables wherein silk and cotton thread wrappingshave been used for insulating the wires, it is often necessary that acable made up in this manner be cut at short intervals when it isrequired that the wires be multipled between similar pieces ofapparatus. At

the portions where the wires are cut, the silk and cotton threads on thewire become frayed and loose from the conductor. The wax with which theconductors have been impregnated does not hold the frayed ends tightlyagainst the conductors after the conductors have been cut and aconsiderable length of the bare copper conductor is exposed, in factmore than is necessary to prop-' erly solder the conductor to itsrequired connection. This frequently results in short circuits.

However, through the use of the acetone treated conductor and thentreated with acetone. Only a single layer of cellulose material 1 may benecessary, although it is desirable that more than one layer 8 and 9,each wound in the opposite directions be provided. Furthermore, eachwrapping by itself may be treated separately with the solution ofacetone, or a plurality of wrappings superimposed upon the conductor 5may be finally treated with the solution. In any event, the total numberof wrappings are each amalgamated by the solution of acetone into asingle homogeneous mass upon the conductor.

The insulation covering for copper wire as disclosed by this invention,may be furthermore provided with a braided tar covering and in additiona rubber composition covering so that it may be utilized for outdoorsignalling use or in any other capacity.

The solution of acetone may be applied to the cellulose wrapping on theconductor 5 by running the wire through a tank containing a quantity ofthe solution. The acetone, after having been applied to the conductor,dries very quickly, after the conductor has been withdrawn from thesolution, and the wire is ready for use.

From the foregoing it is apparent that no baking process is required forexcluding moisture from the conductor or from the cable and furthermorethat the cable constructed according to the invention does not requirefurther insulation as has been previously performed by boiling the cablein a mixture of beeswax or paraflin to further insulate it: The wrappingof cellulose material provides a perfect insulator for the conductor.

While the use of "Rayon or artificial silk has been indicated forwrapping the, conductors, it is to be understood that any othercellulose material or organic compound may be utilized which may bepartially dissolved by a solution of acetone. It is, therefore, notdesired to be limited to the speciflc embodiment of the inventionillustrated and described. but only by the scope of the appended claim.

What is claimed is: g

The method of producing an insulated electric conductor which consistsin applying a coating of enamel to the conductor, in wrappingmultithread strands of cellulose material in layers over said enamel.and in treating the layers of material with a solvent of said materialto thereby amalgamate the material into a homogeneous mass and cause itto adhere to said enamel.

WIILIAM J. HOMER.

